Mommy Boo-Boo Kisses Study

Maternal kissing of boo-boos confers no benefit on children with minor
traumatic injuries compared to both no intervention and sham kissing. In fact, children in the maternal kissing group were significantly more distressed at 5 minutes than were children in the no intervention group. The practice of maternal kissing of boo-boos is not supported by the evidence and we recommend a moratorium on the practice.

Abstract
Background The practice of maternal kissing of minor injuries of childhood (boo-boos),
though widely endorsed and practised, has never been demonstrated to be of benefit to
children.
Objective To determine the efficacy, if any, of maternal kissing of boo-boos in toddlers.
Design Randomized, controlled and double-blinded study of children with experimentally
induced minor injuries. Control arms included both no intervention group and ‘sham’
(non-maternal) kissing. Children were blinded to the identity of the kisser in both the
maternal and sham control groups.
Setting Outpatient research clinics in Ottawa, Canada.
Participants 943 maternal–toddler pairs recruited from the community.
Measurements Toddler Discomfort Index (TDI) pre-injury, 1 and 5 minutes post-injury.
Results One-minute and 5-minute TDI scores did not differ significantly between the
maternal and sham kiss groups. Both of these groups had significantly higher TDI scores
at 5 minutes compared to the no intervention group.
Conclusions Maternal kissing of boo-boos confers no benefit on children with minor
traumatic injuries compared to both no intervention and sham kissing. In fact, children in
the maternal kissing group were significantly more distressed at 5 minutes than were
children in the no intervention group. The practice of maternal kissing of boo-boos is not
supported by the evidence and we recommend a moratorium on the practice.

Introduction
The use of maternal kisses in the treatment of minor injuries
occurring in early childhood (boo-boos) predates the era of
evidence-based medicine by at least several decades. As such,
controlled studies of maternal kissing are rare and, in general,
poorly designed. A recent Cochrane Collaboration systematic
review of maternal kissing in childhood injuries discovered that
most studies lacked sufficient scientific rigor [1]. The authors note
that control groups were often lacking and, when present,
randomization virtually never occurred. In no studies were children blinded to the identity of the kisser. The authors conclude that
‘given the current paucity of data in support of effectiveness, the
practice of mother’s kissing the minor injuries of young children
cannot be supported’ [1].
Nonetheless, maternal kissing of infants and toddler boo-boos
continues to be a common first line therapy. According to the US
Census Bureau, fully 97% of American mothers admitted to kissing
at least one minor childhood injury in 2010 [2]. Furthermore, a
survey of the American Pediatric Association found that 83% of
paediatricians either ‘strongly agreed’ or ‘agreed’ with the statement ‘I encourage mothers to kiss the boo-boos (minor injuries) of

their infants and toddlers’ [3]. Such widespread endorsement of an
unproven intervention bespeaks the untoward propensity of doctors
(at least American doctors) to accept tradition, magical thinking and
expert opinion as a foundation for clinical practice [4].
In an effort to help understand the value, if any, of maternal
kissing in the treatment of minor childhood injuries, we formed the
Study of Maternal and Child Kissing (SMACK) Working Group in
2009. This multi-centred, multidisciplinary group of clinicians and
researchers realized early on that only a randomized, controlled
and blinded study would be able to definitively determine the
efficacy of boo-boo kissing.

Methods
Subjects
Maternal–toddler pairs were solicited through advertisements in
family medicine and paediatric clinics throughout the city of
Ottawa, Canada. Inclusion criteria for children were age between
18 and 36 months and the ability to communicate pain or discomfort through tears or words. Mothers had to be over the age of 18,
English- or French-speaking, and have two lips sufficient in nature
1

Boo-boo kissing

to deliver a palpable kiss. Mothers were excluded if they had oral
ulcers or had ever been indicted or convicted of child abuse or
neglect.
We screened 1368 maternal–pairs, enrolling 943 in the study.
Informed consent was obtained from the mothers prior to enrolment and assent, in the form of a bit of a smile, was obtained from
all toddlers. The study was approved by the Human Subjects
Committee of the SMACK.

Induction of boo-boos
In order to best simulate the types of injuries most often occurring
in toddlers, two different methods of inducing boo-boos were
employed, both of which have been described previously [5]. To
induce head boo-boos, a piece of chocolate was placed under a low
table edge and the child would be allowed to crawl to the candy.
Invariably, the child would then stand to eat the chocolate and
would strike his or her head on the table edge. All tables were
constructed of soft wood (pine or fir) and edges were appropriately
rounded enough to guarantee that skin would not be broken. Hand
boo-boos were induced by placing a favourite object (lovey) of the
child just out of reach on a counter behind a heated coil. Attempts
to obtain the lovey would result in a noxious thermal stimulus to
the fingertips. The coil was heated to 50 degrees Celsius (120 F) in
order to produce a significant but non-damaging stimulus. Each
child was subjected to only one boo-boo during per testing session.
Sessions were separated by 1 week and were held in different
study centres in order to avoid the confounder of child recall.

Randomization and blinding
Prior to the induction of boo-boos, children were randomized to
one of three potential interventions: (1) a maternal kiss of the
injured body part, (2) a non-maternal (sham) kiss of the injured
body part or (3) no intervention. Randomization took place after a
child was secured in the testing facility, and neither investigators
nor mother was aware of the study arm prior to this moment.
Assignment to study arms was determined by a random number
generator at a secure location and relayed to the test site by a
satellite uplink. In the intervention groups, children were blinded
to the identity of their kisser by having them place the injured body
part into an appropriately sized aperture in an opaque screen.
Maternal kisses were delivered in the fashion usual for the mother–
child pair (if applicable) and without verbal embellishment that
might have served to negate the blinding. ‘Sham’ kisses were
delivered by a trained researcher, free of oral ulcers, with a standard 5-second pressing of both lips on the affected body part followed by an exaggerated puckering sound. A third investigator
assessing the child response was also blinded to the intervention,
not beginning the observation period until 30 seconds after the
boo-boo induction and the kiss (in the intervention groups) had
been delivered.

Outcome measures
The effect of the intervention was assessed using the Toddler
Discomfort Index (TDI), a 15-point, five-domain, non-verbal tool
that allows for the quantification of distress in small children [6].
For instance, the domain of auditory expression of discomfort
2

Between group differences assessed by Fisher’s exact test. All differences are non-significant with P > 0.2, except for *where P < 0.05 for
interventions compared with no intervention.

includes the decibel level of crying, the duration of crying and the
length of time from the first expression of discomfort to the crescendo (breathholding coefficient). The TDI has been described in
earlier reports and has been validated in both traumatic injuries
and non-traumatic illnesses [7]. Scores range may range from 0
(no visible distress) to 45 (heart-rending distress). A difference of
5 points is considered clinically significant. All assessments were
made by one of two investigators with extensive experience in
administering the TDI.

Results
In total, 943 maternal–child pairs participated in 1374 boo-boo
inductions. Although the study design called for each maternal–
child pair to participate in two boo-boo inductions each, 512
mothers did not complete the second study session. Reasons for
not completing the second session included the development of
oral ulcers in the mother (1), interim indictment on child neglect
charges (1) and other reasons (510). There was a trend (P = 0.08,
data not shown) for those mothers whose child received the shamkiss intervention in the first testing session to not complete the
second.
Of the 1374 boo-boo inductions, 446 subjects received maternal
kisses, 443 received ‘sham’ kisses and 445 received no intervention. One-minute and 5-minute TDI scores did not differ significantly between the maternal and sham kiss groups. Both of these
groups had significantly higher TDI scores at 5 minutes compared
with the no intervention group (Table 1).

Discussion
This randomized, controlled and blinded study demonstrated no
value to maternal kisses compared to sham kisses in alleviating the
distress of toddlers with boo-boos. In addition, 5 minute scores of
distress were higher in toddlers who had their injured body part
kissed (maternal and ‘sham’) compared with those who received
no intervention. Although this finding suggests that maternal
kissing may actually be worse than no intervention at all, we do
suggest caution in endorsing this conclusion. (It did appear that
requiring children to put their injured head or arm through a dark
aperture may have induced some level of additional stress to some
particularly sensitive children.)
Still, the lack of efficacy of maternal kisses compared with
‘sham’ kisses suggests that, despite being advocated by doctors
and endorsed by virtually all mothers, there is no scientific justification to the practice. Some would likely argue that, given that

maternal kisses did not clearly harm children, the practice is
innocuous. In addition to defying the very tenets of evidence-based
medicine, this argument also fails to recognize potential untoward
effects of maternal kissing of boo-boos. First, the placing of the
lips on the soiled appendages of toddlers likely puts mothers at a
higher risk of acquiring viral and bacteriologic infections. Second,
maternal resources are very limited, and time spent on delivering
ineffective kisses to boo-boos means that maternal attention is not
devoted to other activities that have clearly been shown to be
beneficial to toddlers, such as the introduction of algebraic functions and the teaching of conversational Mandarin [8]. Most
importantly, reliance on ineffective therapies may delay or prevent
the delivery of proven and appropriate medical care, such as BacBe-Gone® antibacterial ointment and Steri-Aids® self-adhesive
bandages [9].
Although brilliant in its simplicity and robust in its design, our
study does have several limitations. First, we only tested children
between the ages of 18 and 36 months, limiting generalizability to
older or younger children. The ages of 18–36 months, however,
represent the peak incidence of boo-boos. In addition, by 5 years
of age, many children, perhaps recognizing the ineffectiveness of
the practice, overtly reject maternal kisses, especially when peers
are present [10]. Our study is also limited in that it only assessed
the effect of maternal kisses on the child. It remains possible that
mothers themselves confer some psychological benefit from a
practice that, at least on its face, appears directed at the child. We
did note that many mothers appeared significantly distraught when
their child was randomized to an intervention other than maternal
kissing. In fact, there is some preliminary evidence to suggest that
maternal sense of self-worth and personal happiness is associated
with attempts to remedy distress in offspring [11,12]. Multiple
emotive comments were directed at researchers throughout the
study that led us to believe that mothers were quite invested in the
kissing process. The study, however, was not designed to investigate this possibility in either a qualitative or quantitative fashion.
More research into the potential psychological effects on mothers
of boo-boo kissing is required.
In summary, maternal kissing of boo-boos is a common practice
that appears to have no ability to reduce the distress of toddlers and
may have significant untoward effects. On the basis of this study,
we recommend a moratorium on the practice.

Boo-boo kissing

Conflict of interest
None declared.

Acknowledgement
Funding provided by The Initiative to Improve Childhood Health.1